U.S. patent application number 11/426736 was filed with the patent office on 2006-12-28 for charge control resin particles and toner for developing electrostatic images.
Invention is credited to Akihide Isoda, Tetsuji Kihara, Tohru Tsuruhara.
Application Number | 20060292471 11/426736 |
Document ID | / |
Family ID | 19187208 |
Filed Date | 2006-12-28 |
United States Patent
Application |
20060292471 |
Kind Code |
A1 |
Isoda; Akihide ; et
al. |
December 28, 2006 |
CHARGE CONTROL RESIN PARTICLES AND TONER FOR DEVELOPING
ELECTROSTATIC IMAGES
Abstract
Charge control resin particles comprising a mixture of at least
a charge control agent and a resin, wherein a crystalline zinc
3,5-di-tert-butylsalicylate represented by General Formula below,
and having major peaks of X-ray diffraction using the
CuK.alpha.-characteristic X-ray at Bragg angles 2.theta. of at
least 6.4.+-.0.2.degree. and 15.4.+-.0.2.degree., is contained as
said charge control agent. Toner for developing electrostatic
images which comprises a coloring agent, a binder resin for toner,
and the charge control resin particles. ##STR1##
Inventors: |
Isoda; Akihide; (Osaka,
JP) ; Kihara; Tetsuji; (Osaka, JP) ;
Tsuruhara; Tohru; (Osaka, JP) |
Correspondence
Address: |
MCGLEW & TUTTLE, PC
P.O. BOX 9227
SCARBOROUGH STATION
SCARBOROUGH
NY
10510-9227
US
|
Family ID: |
19187208 |
Appl. No.: |
11/426736 |
Filed: |
June 27, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10318119 |
Dec 11, 2002 |
|
|
|
11426736 |
Jun 27, 2006 |
|
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Current U.S.
Class: |
430/108.3 ;
430/137.18; 556/132 |
Current CPC
Class: |
G03G 9/09783 20130101;
G03G 9/097 20130101 |
Class at
Publication: |
430/108.3 ;
430/137.18; 556/132 |
International
Class: |
G03G 9/08 20060101
G03G009/08; C07F 3/08 20060101 C07F003/08 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 13, 2001 |
JP |
2001-380621 |
Claims
1. Charge control resin particles comprising a mixture of at least
a charge control agent and a binder resin for toner to form the
resin particle, the mixing ratio by weight of the charge control
agent and the resin being 1:9 to 9:1, wherein a crystalline zinc
3,5-di-tert-butylsalicylate having major peaks of X-ray diffraction
using the CuK.alpha.-characteristic X-ray at Bragg angles 2.theta.
of at least 6.4.+-.0.2.degree. and 15.4.+-.0.2.degree. represented
by General Formula (1) below is contained as said charge control
agent: ##STR3## in Formula (1), t-Bu represents a tert-butyl
group.
2. Charge control resin particles of claim 1 wherein said zinc
3,5-di-tert-butylsalicylate has major peaks of X-ray diffraction
using the CuK.alpha.-characteristic X-ray at Bragg angles 2.theta.
of at least 5.7.+-.0.2.degree., 6.4.+-.0.2.degree. and
15.4.+-.0.2.degree..
3. Charge control resin particles of claim 1 wherein said zinc
3,5-di-tert-butylsalicylate has major peaks of X-ray diffraction
using the CuK.alpha.-characteristic X-ray at Bragg angles 2.theta.
of at least 5.2.+-.0.2.degree., 5.7.+-.0.2.degree.,
6.4.+-.0.2.degree., 6.7.+-.0.2.degree. and 15.4.+-.0.2.degree..
4. Charge control resin particles of claim 1 wherein said zinc
3,5-di-tert-butylsalicylate is obtainable by adding a solution
containing a zinc provider to a solution and/or dispersion liquid
of 3,5-di-tert-butylsalicylic acid to cause a reaction between the
zinc provider and the 3,5-di-tert-butylsalicylic acid.
5. Charge control resin particles of claim 1 wherein said charge
control agent consists essentially of the aforementioned
crystalline zinc 3,5-di-tert-butylsalicylate.
6. Charge control resin particles of claim 1 wherein said charge
control resin particles are cooled, solidified and milled particles
of a thermally kneaded product of the mixture of at least said
charge control agent and said resin.
7. Charge control resin particles of claim 1 consisting essentially
of said binder resin and said charge control agent.
8. Charge control resin particles of claim 1 containing
substantially no coloring agent.
9. Charge control resin particles of claim 1 wherein the average
particle diameter of said charge control resin particles is not
more than 10 .mu.m.
10. Toner for developing electrostatic images, which is prepared
from a coloring agent, a binder resin for toner, and charge control
resin particles, said charge control resin particles comprising a
mixture of at least a binder resin for toner to form the resin
particle and a crystalline zinc 3,5-di-tert-butylsalicylate having
major peaks of X-ray diffraction using the
CuK.alpha.-characteristic X-ray at Bragg angles 2.theta. of at
least 6.4.+-.0.2.degree. and 15.4.+-.0.2.degree. represented by
General Formula (1) below as a charge control agent, said
crystalline zinc 3,5-di-tert-butylsalicylate being dispersed in a
mixture of said binder resin for toner and said binder resin for
toner to form the resin particles: ##STR4## in Formula (1), t-Bu
represents a tert-butyl group.
11. Toner of claim 10 wherein said zinc 3,5-di-tert-butylsalicylate
has major peaks of X-ray diffraction using the
CuK.alpha.-characteristic X-ray at Bragg angles 2.theta. of at
least 5.7.+-.0.2.degree., 6.4.+-.0.2.degree. and
15.4.+-.0.2.degree..
12. Toner of claim 10 wherein said zinc 3,5-di-tert-butylsalicylate
has major peaks of X-ray diffraction using the
CuK.alpha.-characteristic X-ray at Bragg angles 2.theta. of at
least 5.2.+-.0.2.degree., 5.7.+-.0.2.degree., 6.4.+-.0.2.degree.,
6.7.+-.0.2.degree. and 15.4.+-.0.2.degree..
13. Toner of claim 10 wherein said zinc 3,5-di-tert-butylsalicylate
is obtainable by adding a solution containing a zinc provider to a
solution and/or dispersion liquid of 3,5-di-tert-butylsalicylic
acid to cause a reaction between the zinc provider and the
3,5-di-tert-butylsalicylic acid.
14. Toner of claim 10 wherein the charge control resin particles
consist essentially of said binder resin for toner to form the
resin particle and charge control agent.
15. Toner of claim 10 wherein the charge control resin particles
contain substantially no coloring agent.
16. Toner of claim 10 wherein the mixing ratio by weight of the
charge control agent and the resin in the charge control resin
particles is 1:9 to 9:1.
17. Process for manufacturing toner for developing electrostatic
images comprising: mixing at least charge control resin particles
which are cooled, solidified and milled particles of a thermally
kneaded mixture of at least a binder resin for toner to form the
resin particle and a charge control agent, a coloring agent and a
binder resin for toner, wherein an active ingredient of said charge
control agent is a crystalline zinc 3,5-di-tert-butylsalicylate
having major peaks of X-ray diffraction using the
CuK.alpha.-characteristic X-ray at Bragg angles 2.theta. of at
least 6.4.+-.0.2.degree. and 15.4.+-.0.2.degree. represented by
General Formula (1) below; kneading the mixture in a molten state;
and cooling, solidifying and then pulverizing the mixture to obtain
a toner containing the charge control agent dispersed in a mixture
of said binder resin for toner and said binder resin for toner to
form the resin particles: ##STR5## in Formula (1), t-Bu represents
a tert-butyl group.
18. Process of claim 17 wherein said zinc
3,5-di-tert-butylsalicylate is obtainable by adding a solution
containing a zinc provider to a solution and/or dispersion liquid
of 3,5-di-tert-butylsalicylic acid to cause a reaction between the
zinc provider and the 3,5-di-tert-butylsalicylic acid.
19. Process of claim 17 wherein the charge control resin particles
consist essentially of said binder resin and charge control
agent.
20. Process of claim 17 wherein the charge control resin particles
contain substantially no coloring agent.
21. Process of claim 17 wherein the mixing ratio by weight of the
charge control agent and the resin in the charge control resin
particles is 1:9 to 9:1.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application under 37 CFR
1.53(b) of pending prior application Ser. No. 10/318,119 filed Dec.
12, 2002.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a toner for developing
electrostatic images permitting the control of the charge amount of
a toner used to develop electrostatic latent images in
electrophotography, electrostatic recording, electrostatic printing
and others, and charge control resin particles used as a raw
material for the production of the same toner.
[0004] 2. Description of the Prior Art
[0005] In copying machines and other equipment based on
electrophotography, various dry or wet toners containing a coloring
agent, a fixing resin and other substances are used to visualize
the electrostatic latent image formed on the photoreceptor having a
photosensitive layer containing an inorganic or organic
photoconductive substance. The chargeability of such toners is the
most important factor in electrostatic latent image developing
systems. Thus, to appropriately control the charge amount of toner,
a charge control agent providing a positive or negative charge is
often added to the toner.
[0006] Charge control agents providing a positive charge for toner
in actual application include the nigrosine dyes disclosed in
Japanese Patent Examined Publication No. SHO41-2427 and elsewhere.
Charge control agents providing a negative charge for toner in
actual application include the metal complex dyes disclosed in
Japanese Patent Examined Publication Nos. SHO41-20153, SHO43-17955,
SHO45-26478 and elsewhere. However, most of the charge control
agents described above are structurally complex and unstable; for
example, they are likely to be decomposed or deteriorated to lose
their initial charge control performance when exposed to mechanical
friction or impact, temperature or humidity changes, electric
impact, light irradiation, etc. Also, many of such conventional
charge control agents are colored so that they are unsuitable for
use in full-color toners.
[0007] As a means for resolving these problems, Japanese Patent
Laid-Open No. SHO62-145255, for example, discloses the containment
of a metal salt of salicylic acid or a derivative thereof as a
charge control agent. Japanese Patent Laid-Open No. SHO63-163374
proposes methods for determining the crystalline structures and
crystalline diameters of metal salts of salicylic acid and
derivatives thereof to be contained in the toner, with particular
mention of zinc 3,5-di-tert-butylsalicylate. Although these
substances are advantageous in that they can be used in color
toners, their heat stability, uniform dispersibility in resin, or
charge control performance, or charging rise speed, in particular,
is insufficient so that they remain to be investigated further.
[0008] The present invention was developed in view of the
aforementioned problems in the prior art and is intended to provide
a toner for developing electrostatic images wherein the charge
control agent contained therein possesses good heat resistance,
good affinity for resin and good dispersibility in resin, which
exhibits a high speed of charging rise, which is excellent in
charge stability to temperature and humidity changes (environmental
resistance) and charge characteristic stability over time (storage
stability), and which can be used in various chromatic or
achromatic toners, and charge control resin particles used as a
starting material for the production of said toner.
SUMMARY OF THE INVENTION
[0009] Resolving the above problems, the charge control resin
particles of the present invention are charge control resin
particles comprising at least a charge control agent and a resin,
wherein the charge control agent contained therein is [0010] [A] a
crystalline zinc 3,5-di-tert-butylsalicylate represented by General
Formula (1) below, and having major peaks of X-ray diffraction
using the CuK.alpha.-characteristic X-ray (wavelength 1.541 .ANG.)
at Bragg angles 2.theta. of at least 6.4.+-.0.2.degree. and
15.4.+-.0.2.degree. or [0011] [B] a crystalline zinc
3,5-di-tert-butylsalicylate represented by General Formula (1)
below, and having major peaks of X-ray diffraction using the
CuK.alpha.-characteristic X-ray (wavelength 1.541 .ANG.) at Bragg
angles 2.theta. of at least 7.7.+-.0.2.degree. and
15.7.+-.0.2.degree.. ##STR2## in Formula (1), t-Bu represents a
tert-butyl group.
[0012] When preparing a toner for developing electrostatic images
using the charge control resin particles of the present invention,
a coloring agent and a binder resin for toner, the crystalline zinc
3,5-di-tert-butylsalicylate contained in the charge control resin
particles is highly uniformly dispersed in the resin so that its
charge control performance is improved. In particular, reverse
charging in the initial stage of the frictional charging of the
toner and charge variation over time can be prevented.
[0013] The toner of the present invention for developing
electrostatic images, which comprises the charge control resin
particles of the present invention, a coloring agent and a binder
resin for toner, is a toner wherein the charge control agent
contained therein possesses good heat resistance, good affinity for
resin and good dispersibility in resin and ensures a high speed of
charging rise, it is highly effective in increasing the speed in
electrophotographic and other processes and improving the quality
of initial images thereof, is excellent in charge stability to
temperature and humidity changes (environmental resistance) and
charge characteristic stability over time (storage stability), and
can be used in various chromatic or achromatic toners.
[0014] The aforementioned zinc 3,5-di-tert-butylsalicylate can be
prepared providing zinc to the starting material
3,5-di-tert-butylsalicylic acid obtained by butylation of salicylic
acid.
[0015] If the 3,5-di-tert-butylsalicylic acid is zincified by a
reaction in an aqueous system, the crystalline zinc
3,5-di-tert-butylsalicylate of [A] above can be obtained by steps
[1] to [4] below. Although it can also be obtained by a reaction
using an organic solvent system, an aqueous reaction is preferred
from the viewpoint of cost and safety. [0016] [1] Step for
dissolving 3,5-di-tert-butylsalicylic acid in an alkaline aqueous
solution. [0017] [2] Step for dissolving a zinc provider in water.
[0018] [3] Reaction step wherein the aqueous solution of a zinc
provider obtained in step [2] is added to the aqueous solution of
3,5-di-tert-butylsalicylic acid obtained in step [1], while heating
the latter, and the mixture is stirred with heating until the
reaction is completed. [0019] [4] Post-treatment step for filtering
the reaction mixture obtained in step [3] and washing, drying and
then milling the cake filtered off.
[0020] Specifically, the desired product can, for example, be
synthesized by the following method. A sufficient amount of an
alkaline aqueous solution is added to 2 mol of
3,5-di-tert-butylsalicylic acid and dissolved with heating.
Separately, an aqueous solution incorporating 1 mol of a zinc
provider is prepared. This solution is added drop by drop to the
aforementioned aqueous solution of 3,5-di-tert-butylsalicylic acid,
while heating the latter aqueous solution, to cause the reaction
with heating and pH adjustment; after completion of the reaction,
the reaction mixture is filtered and the cake filtered off is
washed with water and dried.
[0021] Examples of zinc providers used to zincify
3,5-di-tert-butylsalicylic acid include, but are not limited to,
zinc sulfate, zinc chloride and zinc acetate and so on.
[0022] As preferable examples of the crystalline zinc
3,5-di-tert-butylsalicylate of [A] above which can be obtained by
these steps, there may be mentioned [0023] a crystalline zinc
3,5-di-tert-butylsalicylate having major peaks of X-ray diffraction
using the CuK.alpha.-characteristic X-ray at Bragg angles 2.theta.
of at least 5.7.+-.0.2.degree., 6.4.+-.0.2.degree. and
15.4.+-.0.2.degree.; and [0024] a crystalline zinc
3,5-di-tert-butylsalicylate having major peaks of X-ray diffraction
using the CuK.alpha.-characteristic X-ray at Bragg angles 2.theta.
of at least 5.2.+-.0.2.degree., 5.7.+-.0.2.degree.,
6.4.+-.0.2.degree., 6.7.+-.0.2.degree. and 15.4.+-.0.2.degree..
[0025] If the zinc 3,5-di-tert-butylsalicylate is zincified by a
reaction in an aqueous system, the crystalline zinc
3,5-di-tert-butylsalicylate of [B] above can be obtained by steps
[1], [2], [3]' and [4] wherein step [3] above is replaced with
reaction step [3]' wherein the aqueous solution of
3,5-di-tert-butylsalicylic acid obtained in step [1] is added to
the aqueous solution of a zinc provider obtained in step [2], while
heating the latter, and the mixture is stirred with heating until
the reaction is completed.
[0026] Specifically, the desired product can, for example, be
synthesized by the following method. A sufficient amount of an
alkaline aqueous solution is added to 2 mol of
3,5-di-tert-butylsalicylic acid and dissolved with heating.
Separately, an aqueous solution incorporating 1 mol of a zinc
provider is prepared. While heating this aqueous solution, the
aforementioned aqueous solution of 3,5-di-tert-butylsalicylic acid
is added drop by drop, and the reaction is carried out with heating
and pH adjustment; after completion of the reaction, the reaction
mixture is filtered and the cake filtered off is washed with water
and dried. As example zinc providers, there may be mentioned those
mentioned above.
[0027] As a preferable example of the crystalline zinc
3,5-di-tert-butylsalicylate of [B] above, which can be obtained by
these steps, there may be mentioned a crystalline zinc
3,5-di-tert-butylsalicylate having major peaks of X-ray diffraction
using the CuK.alpha.-characteristic X-ray at Bragg angles 2.theta.
of 5.2.+-.0.2.degree., 6.7.+-.0.2.degree., 7.7.+-.0.2.degree. and
15.7.+-.0.2.degree..
[0028] The crystalline zinc 3,5-di-tert-butylsalicylate of [B]
(especially that obtained by steps [1], [2], [3]' and [4]) can be
obtained as a charge control agent having a great amount of initial
charges, a good charge control characteristic, and an appropriately
low bulk density of the zinc 3,5-di-tert-butylsalicylate particles
(e.g., 2 to 5 ml/g). For this reason, it improves the
dispersibility in resins such as resins for toner, making it easy
to uniformly disperse in the resin, increasing the toner charging
rise speed, and improving charge stability to temperature and
humidity changes (environmental resistance) and charge
characteristic stability over time (storage stability), and it can
be transported with an increased mass per unit volume so that the
transportation cost can be reduced significantly.
[0029] The charge control agent in the present invention may
consist essentially of the aforementioned crystalline zinc
3,5-di-tert-butylsalicylate.
[0030] The aforementioned charge control resin particles may be
solidified milled particles of a thermally kneaded product of the
mixture of at least a charge control agent and a resin. Such charge
control resin particles can, for example, be obtained by mixing a
charge control agent and a resin (e.g., binder resin) at a given
ratio, heating and kneading the mixture, and cooling, solidifying
and milling the resin composition thus obtained.
[0031] The mixing ratio by weight of the charge control agent
(e.g., crystalline zinc 3,5-di-tert-butylsalicylate of [A] or [B]
above) and the resin (e.g., binder resin) in the charge control
resin particles of the present invention may preferably be 1:9 to
9:1, more preferably 3:7 to 7:3.
[0032] The toner of the present invention for developing
electrostatic images is a toner for developing electrostatic images
comprising the aforementioned charge control resin particles, a
coloring agent and a binder resin for toner, or a toner for
developing electrostatic images comprising a charge control agent,
a coloring agent and a binder resin for toner, wherein a
crystalline zinc 3,5-di-tert-butylsalicylate represented by General
Formula (1) above, and having major peaks of X-ray diffraction
using the CuK.alpha.-characteristic X-ray at Bragg angles 2.theta.
of at least 5.2.+-.0.2.degree., 6.7.+-.0.2.degree.,
7.7.+-.0.2.degree. and 15.7.+-.0.2.degree., is contained as the
charge control agent.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] FIG. 1 shows an X-ray diffraction chart of the charge
control agent of Example 1.
[0034] FIG. 2 shows an X-ray diffraction chart of the charge
control agent of Example 2.
[0035] FIG. 3 shows an X-ray diffraction chart of the charge
control agent of Example 3.
DETAILED DESCRIPTION OF THE INVENTION
[0036] Charge Control Resin Particles
[0037] Although the particle diameter of the crystalline zinc
3,5-di-tert-butylsalicylate in the present invention is not subject
to limitation, it is desirable that the average particle diameter
be not more than 20 .mu.m, preferably not more than 10 .mu.m, from
the viewpoint of the improvement of its dispersibility in
resin.
[0038] Desired crystalline transformation for the zinc
3,5-di-tert-butylsalicylate in the present invention can, for
example, be achieved by wet and/or dry dispersion milling or
solvent treatment.
[0039] The crystalline zinc 3,5-di-tert-butylsalicylate (charge
control agent) in the present invention surpasses conventional
salicylic acid metal salts in dispersibility in resin. When
preparing the charge control resin particles of the present
invention by mixing this crystalline zinc
3,5-di-tert-butylsalicylate and a resin, and preparing a toner for
developing electrostatic images by mixing the charge control resin
particles, a coloring agent and a binder resin for toner, the
aforementioned crystalline zinc 3,5-di-tert-butylsalicylate in the
present invention is more uniformly dispersed in the resin so that
its charge control performance is improved. In particular, reverse
charging in the initial stage of the frictional charging of the
toner and charge variation over time can be prevented.
[0040] Examples of resins which can be used in the charge control
resin particles of the present invention include the commonly known
binder resins for toner described below. A resin preferably used in
charge control resin particles is a resin having a number-average
molecular weight (Mn) of 2500 to 30000, preferably a resin having a
weight-average molecular weight (Mw)/number-average molecular
weight (Mn) ratio in the range from 2 to 20. The resin in charge
control resin particles and the resin used to prepare a toner using
the same charge control resin particles may be identical or
not.
[0041] The charge control resin particles of the present invention
are, for example, produced as described below. Specifically, charge
control resin particles can be obtained by thoroughly mixing at
least a charge control agent and a resin in a Henschel mixer or
another mechanical mixer, and subsequently kneading the mixture in
a molten state under normal or increased pressure in a hot kneader
such as a heat roll, a kneader or an extruder, cooling, solidifying
and then milling the mixture.
[0042] The charge control agent used in the production of the
charge control resin particles of the present invention may, for
example, be in the form of a dry powder or a pre-drying aqueous
pressed cake. When using a charge control agent in a dry powder
form, a dispersion aid or an additive may be added to improve its
dispersibility in resin. For example, water or any organic solvent
may be used. Specifically, after the charge control agent of the
present invention, a resin and water or any organic solvent are
mixed in a Henschel mixer or another mechanical mixer, the mixture
is charged and kneaded in a heat roll, a flasher, a kneader, an
extruder, or the like. Alternatively, when using a flasher, a
kneader, or the like, it is possible to charge and mix the charge
control agent, resin and water or any organic solvent in a single
step at one time. Subsequently, the mixture is kneaded in a molten
state with heating under increased or normal pressure. The
remaining water or solvent is then evaporated off under normal or
reduced pressure to dry the mixture. The mixture is cooled,
solidified and then milled to yield charge control resin particles.
Although the aforementioned organic solvent may be a commonly known
organic solvent, it is preferable to use a low-boiling highly
volatile solvent such as ethanol, methanol, isopropanol or
acetone.
[0043] Toner for Developing Electrostatic Images
[0044] The toner of the present invention for developing
electrostatic images comprises a charge control agent [a
crystalline zinc 3,5-di-tert-butylsalicylate represented by General
Formula (1) above, and having major peaks of X-ray diffraction
using the CuK.alpha.-characteristic X-ray at Bragg angles 2.theta.
of at least 5.2.+-.0.2.degree., 6.7.+-.0.2.degree.,
7.7.+-.0.2.degree. and 15.7.+-.0.2.degree.] or the charge control
resin particles of the present invention, a binder resin for toner
and a coloring agent.
[0045] The amount of charge control agent incorporated in the toner
of the present invention for developing electrostatic images may be
0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight per
100 parts by weight of the binder resin for toner (or the sum of
the binder resin for toner and the resin in the charge control
resin particles).
[0046] Examples of resins which can be used in the toner of the
present invention include resins that have traditionally been used
as binder resins for toners. Specifically, there may be mentioned
synthetic resins such as polystyrene resin, styrene-acrylic resin,
styrene-butadiene resin, styrene-maleic resin, styrene-vinyl methyl
ether resin, styrene-methacrylate copolymer, polyester resin,
phenol resin and epoxy resin. These resins may be used singly or in
blends of several kinds. Of these resins, those having a glass
transition point of 50 to 75.degree. C., a softening point of 80 to
150.degree. C. and a number-average molecular weight of 1000 to
30000 are preferred, with greater preference given to those wherein
the weight-average molecular weight/number-average molecular weight
ratio is 2 to 50.
[0047] For preferable use of a binder resin for toner and a resin
in charge control resin particles in a toner used for full-color
imaging by subtractive color mixture or for OHP (overhead
projectors) etc., the resin or binder resin is required to have
special properties, for example, it should be transparent,
substantially colorless (no tone damage occurs in the toner image),
compatible with the charge control agent used, fluid under
appropriate heat or pressure, and pulverizable. Examples of such
resins for preferable use include polystyrene resin, acrylic resin,
styrene-acrylic resin, styrene-methacrylate copolymer and polyester
resin. A polyester resin or styrene-acrylic resin having an acid
value of 1 to 50 mg KOH/g, in particular, is preferred.
[0048] The toner of the present invention may incorporate various
known dyes and pigments as coloring agents. Examples of such dyes
or pigments which can be used in color toners include carbon black,
organic pigments such as quinophthalone, Hansa Yellow, Rhodamine 6G
Lake, quinacridone, Rose Bengale, copper Phthalocyanine Blue and
copper Phthalocyanine Green, various oil-soluble dyes or disperse
dyes such as azo dyes, quinophthalone dyes, anthraquinone dyes,
xanthene dyes, triphenylmethane dyes and phthalocyanine dyes, and
dyes and pigments modified with higher fatty acids, synthetic
resins, or the like.
[0049] The toner of the present invention for developing
electrostatic images may incorporate the aforementioned coloring
agents singly or in combination. Dyes and pigments having good
spectral characteristics can be preferably used to prepare toners
of the three primaries for full-color imaging. Chromatic monocolor
toners may incorporate an appropriate combination of a pigment and
dye of the same color tone, such as a rhodamine pigment and dye, a
quinophthalone pigment and dye, or a phthalocyanine pigment and
dye, as coloring agents.
[0050] Also, to improve toner quality, additives, e.g., anti-offset
agents, fluidity-improving agents (e.g., various metal oxides such
as silica, aluminum oxide and titanium oxides, magnesium fluoride,
etc.) and cleaning aids (e.g., metal soaps of stearic acid etc.;
various synthetic resin microparticles such as fluorine-series
synthetic resin microparticles, silicone-series synthetic resin
microparticles and styrene-(meth)acrylic synthetic resin
microparticles), can be added internally or externally.
[0051] Anti-offset agents (releasing agents) used to improve toner
fixability as described above include various waxes, particularly
those having average molecular weights of 500 to 15000.
Specifically, there can be used polyolefin type waxes such as low
molecular polypropylene, polyethylene, oxidized polypropylene and
oxidized polyethylene; and natural waxes such as carnauba wax, rice
wax and montan wax.
[0052] The toner of the present invention for developing
electrostatic images is, for example, produced as described below.
A toner having an average particle size of 5 to 20 .mu.m is
obtained by thoroughly mixing a binder resin for toner and coloring
agent a charge control agent or charge control resin particles as
described above, and, if necessary, a magnetic material, a
fluidizing agent and other additives, using a ball mill or another
mechanical mixer, subsequently kneading the mixture in a molten
state using a hot kneader such as a heat roll, a kneader or an
extruder, cooling, solidifying and then pulverizing the mixture,
and classifying the particles.
[0053] Other usable methods include the method in which the
starting materials are dispersed in a binder resin solution and
then spray dried, and the polymerizing toner production method in
which a given set of starting materials are mixed in a monomer for
binder resin to yield an emulsified suspension which is then
polymerized to yield the desired toner (e.g., the method described
in Japanese Patent Laid-Open No. HEI1-260461 and Japanese Patent
Laid-Open No. HEI2-32365). When using the toner of the present
invention as a two-component developer, development can be achieved
by the two-component magnetic brush developing process or another
process using the toner in mixture with a carrier powder.
[0054] Any known carrier can be used. Examples of the carrier
include iron powder, nickel powder, ferrite powder and glass beads
about 50 to 200 .mu.m in particle diameter, and such materials as
coated with acrylate copolymer, styrene-acrylate copolymer,
silicone resin, polyamide resin, ethylene fluoride resin or the
like.
[0055] When using the toner of the present invention as a
one-component developer, a fine powder of a ferromagnetic material
such as iron powder, nickel powder or ferrite powder may be added
and dispersed in preparing the toner as described above. Examples
of developing processes which can be used in this case include
contact development and jumping development.
EXAMPLES
[0056] The present invention is hereinafter described in more
detail by means of the following examples, but these are not to be
construed as limitative on the present invention. In the
description below, "part(s) by weight" are referred to as "part(s)"
for short.
[0057] Examples 1 through 5 pertain to the production of charge
control resin particles.
Example 1
[0058] Polyester resin [Diacron ER561 (trade name), produced by
Mitsubishi Chemical Corporation] . . . 50 parts [0059] Charge
control agent (crystalline zinc 3,5-di-tert-butylsalicylate having
major peaks of X-ray diffraction using the
CuK.alpha.-characteristic X-ray [wavelength 1.541 .ANG.] at Bragg
angles 2.theta. of 5.7.+-.0.2.degree., 6.4.+-.0.2.degree. and
15.4.+-.0.2.degree.; an X-ray diffraction chart shown in FIG. 1) .
. . 50 parts [0060] Methanol . . . 10 parts
[0061] The above ingredients were charged in a kneader and mixed
for 15 minutes to moisten the polyester resin powder and charge
control agent with the methanol, after which this mixture was
kneaded in a molten state while the methanol was evaporated by
gradual heating. After cooling, this mixture was further kneaded
with a pair of heat rolls and cooled, and then roughly crushed in a
vibration mill to yield charge control resin particles 1.
[0062] Production of the Aforementioned Charge Control Agent
[0063] 25.0 g of 3,5-di-tert-butylsalicylic acid (0.10 mol obtained
by butylation of salicylic acid) was dissolved in 200 ml of a 2%
aqueous solution of NaOH and heated to about 70.degree. C.
Separately, 14.4 g (0.05 mol) of zinc sulfate heptahydrate was
dissolved in 200 ml of water. This aqueous solution of zinc sulfate
was added drop by drop to the aforementioned aqueous solution of
3,5-di-tert-butylsalicylic acid over a period of about 30 minutes.
Subsequently, after the reaction was carried out at 70 to
80.degree. C. for 2 hours, the reaction mixture was adjusted to a
pH of 7.0.+-.0.5 to complete the reaction.
[0064] This reaction solution was filtered while it remained hot,
and the cake filtered off was washed with water and dried to yield
27.3 g of a white fine powder. The bulk density of this white
powder was 6.9 ml/g. Analysis of the thus-obtained white powder
using a powder X-ray diffraction apparatus detected major peaks of
X-ray diffraction using the CuK.alpha.-characteristic X-ray
[wavelength 1.541 .ANG.] at Bragg angles 2.theta. of
5.7.+-.0.2.degree., 6.4.+-.0.2.degree. and 15.4.+-.0.2.degree..
[0065] In the present and following Examples, X-ray diffraction
analysis of crystalline zinc 3,5-di-tert-butylsalicylate was
conducted using the apparatus shown below on the undermentioned
condition. [0066] Instrumentation: MXP-18 X-ray diffraction
apparatus (manufactured by MAC SCIENCE K.K.) [0067] Target: Cu
[0068] Wavelength: 1.5405 .ANG. (CuK.alpha.1) [0069] Voltage and
current: 40.0 kV, 200 mA [0070] Divergence slit: 1.0.degree. [0071]
Receiving slit: 0.30 mm [0072] Scattering slit: 1.0.degree. [0073]
Scanning speed: 4.0 deg/min
Example 2
[0074] Charge control resin particles 2 were prepared in the same
manner as Example 1, except that the zinc
3,5-di-tert-butylsalicylate of Example 1 was replaced with a
crystalline zinc 3,5-di-tert-butylsalicylate having major peaks of
X-ray diffraction using the CuK.alpha.-characteristic X-ray
[wavelength 1.541 .ANG.] at Bragg angles 2.theta. of at least
5.2.+-.0.2.degree., 5.7.+-.0.2.degree., 6.4.+-.0.2.degree.,
6.7.+-.0.2.degree. and 15.4.+-.0.2.degree. (X-ray diffraction chart
shown in FIG. 2).
Example 3
[0075] Charge control resin particles 3 were prepared in the same
manner as Example 1, except that the zinc
3,5-di-tert-butylsalicylate of Example 1 was replaced with a
crystalline zinc 3,5-di-tert-butylsalicylate having major peaks of
X-ray diffraction using the CuK.alpha.-characteristic X-ray
[wavelength 1.541 .ANG.] at Bragg angles 2.theta. of at least
5.2.+-.0.2.degree., 6.7.+-.0.2.degree., 7.7.+-.0.2.degree. and
15.7.+-.0.2.degree. (X-ray diffraction chart shown in FIG. 3).
[0076] Production of the Aforementioned Charge Control Agent
[0077] 14.4 g (0.05 mol) of zinc sulfate heptahydrate was dissolved
in 200 ml of water. Separately, 25.0 g of
3,5-di-tert-butylsalicylic acid (0.10 mol obtained by butylation of
salicylic acid) was dissolved in 200 ml of a 2% aqueous solution of
NaOH and heated to about 70.degree. C. This aqueous solution of
3,5-di-tert-butylsalicylic acid was added drop by drop to the
aforementioned aqueous solution of zinc sulfate over a period of
about 30 minutes. Subsequently, after the reaction was carried out
at 70 to 80.degree. C. for 2 hours, the reaction mixture was
adjusted to a pH of 7.0.+-.0.5 to complete the reaction.
[0078] This reaction solution was filtered while it remained hot,
and the cake filtered off was washed with water and dried to yield
27.5 g of a white fine powder. The bulk density of this white
powder was 3.0 ml/g. Analysis of the thus-obtained white powder
using a powder X-ray diffraction apparatus detected major peaks of
X-ray diffraction using the CuK.alpha.-characteristic X-ray
[wavelength 1.541 .ANG.] at Bragg angles 2.theta. of
5.2.+-.0.2.degree., 6.7.+-.0.2.degree., 7.7.+-.0.2.degree. and
15.7.+-.0.2.degree..
Example 4
[0079] Styrene-acrylic copolymer resin [ALMATEX CPR600B (trade
name), produced by Mitsui Chemicals, Inc.] . . . 70 parts [0080]
Charge control agent (crystalline zinc 3,5-di-tert-butylsalicylate
having major peaks of X-ray diffraction using the
CuK.alpha.-characteristic X-ray [wavelength 1.541 .ANG.] at Bragg
angles 2.theta. of 5.7.+-.0.2.degree., 6.4.+-.0.2.degree. and
15.4.+-.0.2.degree.) . . . 30 parts
[0081] The above ingredients were uniformly pre-mixed in a Henschel
mixer, after which this mixture was kneaded in a molten state using
a kneader. After cooling, this mixture was further kneaded with a
pair of heat rolls and cooled, and then roughly crushed in a
vibration mill to yield charge control resin particles 4.
Example 5
[0082] Charge control resin particles 5 were prepared in the same
manner as Example 4, except that the zinc
3,5-di-tert-butylsalicylate of Example 4 was replaced with a
crystalline zinc 3,5-di-tert-butylsalicylate having major peaks of
X-ray diffraction using the CuK.alpha.-characteristic X-ray
[wavelength 1.541 .ANG.] at Bragg angles 2.theta. of at least
5.2.+-.0.2.degree., 6.7.+-.0.2.degree., 7.7.+-.0.2.degree. and
15.7.+-.0.2.degree..
[0083] Examples 6 through 10 and Comparative Example 1 pertain to
toner for developing electrostatic images.
Example 6
[0084] Polyester resin [Diacron ER561 (trade name), produced by
Mitsubishi Chemical Corporation] . . . 100 parts [0085] Carbon
black [MA-100 (trade name), produced by Mitsubishi Chemical
Corporation] . . . 6 parts [0086] Low polymer polypropylene [Viscol
550-P (trade name), produced by Sanyo Chemical Industries, Ltd.] .
. . 5 parts [0087] Charge control resin particles 1 obtained in
Example 1 . . . 2 parts
[0088] The above ingredients were uniformly pre-mixed using a
high-speed mixer. This premix was then kneaded in a molten state
using an extruder, cooled and thereafter roughly milled using a
vibration mill. The rough milling product obtained was finely
pulverized using an air jet mill equipped with a classifier to
yield a negatively chargeable black toner 10 to 20 .mu.m in
particle diameter. Five parts of this toner was admixed with 95
parts of an iron powder carrier (TEFV 200/300 (trade name),
produced by Powdertech Co., Ltd.) to yield a developer.
[0089] This developer was measured in a polyethylene bottle. This
bottle was rotated under standard conditions (20.degree. C.-60% RH)
in a ball mill at a rotation rate of 100 rpm to stir and charge the
developer, and changes over time in the charge amount of the
developer were determined. The results of the determination of
changes over time in the charge amount are shown in Table 1.
[0090] Separately, this developer was measured in a polyethylene
bottle. This bottle was rotated in each of a low-temperature
low-humidity (5.degree. C.-30% RH) atmosphere and a
high-temperature high-humidity (35.degree. C.-90% RH) atmosphere in
a ball mill at a rotation rate of 100 rpm for 10 minutes to stir
and charge the developer, and changes over time in the charge
amount of the developer in each case were determined. The results
of the determination of the environmental stability of the charge
amount are shown in Table 2.
[0091] Changes Over Time in Charge Amount TABLE-US-00001 TABLE 1
Time (min) 1 3 5 10 15 30 Charge amount (-.mu.C/g) 30.0 31.9 33.5
36.0 38.0 38.5
[0092] Environmental Stability TABLE-US-00002 TABLE 2 5.degree. C.
- 30% RH 35.degree. C. - 90% RH Charge amount 38.2 38.0
(-.mu.C/g)
[0093] When this developer was used to form toner images using a
commercial copying machine (selenium drum type), fogging-free
high-quality images with good thin line reproducibility and good
charge stability and sustainability without image density reduction
were obtained. The offset phenomenon was never observed.
Example 7
[0094] Styrene-acrylic copolymer resin [ALMATEX CPR600B (trade
name), produced by Mitsui Chemicals, Inc.] . . . 100 parts [0095]
Carbon black [MA-100 (trade name), produced by Mitsubishi Chemical
Corporation] . . . 6 parts [0096] Low polymer polypropylene [Viscol
550-P (trade name), produced by Sanyo Chemical Industries, Ltd.] .
. . 5 parts [0097] Charge control resin particles 1 obtained in
Example 1 . . . 2 parts
[0098] The above ingredients were treated in the same manner as
Example 6 to yield a negatively chargeable black toner 10 to 20
.mu.m in particle diameter and a developer. Using this developer,
changes over time in charge amount and the environmental stability
of charge amount were determined in the same manner as Example 6.
The results are shown in Tables 3 and 4, respectively.
[0099] Changes Over Time in Charge Amount TABLE-US-00003 TABLE 3
Time (min) 1 3 5 10 15 30 Charge amount (-.mu.C/g) 21.5 23.3 24.1
24.7 25.0 26.5
[0100] Environmental Stability TABLE-US-00004 TABLE 4 5.degree. C.
- 30% RH 35.degree. C. - 90% RH Charge amount 26.5 25.6
(-.mu.C/g)
[0101] When this developer was used to form toner images using a
commercial copying machine (selenium drum type), fogging-free
high-quality images with good thin line reproducibility and good
charge stability and sustainability without image density reduction
were obtained. The offset phenomenon was never observed.
Example 8
[0102] Polyester resin [Diacron ER561 (trade name), produced by
Mitsubishi Chemical Corporation] . . . 100 parts [0103] Carbon
black [MA-100 (trade name), produced by Mitsubishi Chemical
Corporation] . . . 6 parts [0104] Low polymer polypropylene [Viscol
550-P (trade name), produced by Sanyo Chemical Industries, Ltd.] .
. . 5 parts [0105] Charge control resin particles 2 obtained in
Example 2 . . . 2 parts
[0106] The above ingredients were treated in the same manner as
Example 6 to yield a negatively chargeable black toner 10 to 20
.mu.m in particle diameter and a developer. Using this developer,
changes over time in charge amount and the environmental stability
of charge amount were determined in the same manner as Example 6.
The results are shown in Tables 5 and 6, respectively.
[0107] Changes Over Time in Charge Amount TABLE-US-00005 TABLE 5
Time (min) 1 3 5 10 15 30 Charge amount (-.mu.C/g) 33.2 34.5 35.6
36.9 37.5 38.0
[0108] Environmental Stability TABLE-US-00006 TABLE 6 5.degree. C.
- 30% RH 35.degree. C. - 90% RH Charge amount 37.7 37.0
(-.mu.C/g)
[0109] When this developer was used to form toner images using a
commercial copying machine (selenium drum type), fogging-free
high-quality images with good thin line reproducibility and good
charge stability and sustainability without image density reduction
were obtained. The offset phenomenon was never observed.
Example 9
[0110] Polyester resin [Diacron ER561 (trade name), produced by
Mitsubishi Chemical Corporation] . . . 100 parts [0111] Oil-soluble
magenta dye [Oil Pink #312(trade name), produced by Orient Chemical
Industries, Ltd.] . . . 6 parts [0112] Low polymer polypropylene
[Viscol 550-P (trade name), produced by Sanyo Chemical Industries,
Ltd.] . . . 5 parts [0113] Charge control resin particles 3
obtained in Example 3 . . . 2 parts
[0114] The above ingredients were treated in the same manner as
Example 6 to yield a negatively chargeable magenta toner 10 to 20
.mu.m in particle diameter and a developer. Using this developer,
changes over time in charge amount and the environmental stability
of charge amount were determined in the same manner as Example 6.
The results are shown in Tables 7 and 8, respectively.
[0115] Changes Over Time in Charge Amount TABLE-US-00007 TABLE 7
Time (min) 1 3 5 10 15 30 Charge amount (-.mu.C/g) 37.0 38.5 39.0
39.4 39.7 40.3
[0116] Environmental Stability TABLE-US-00008 TABLE 8 5.degree. C.
- 30% RH 35.degree. C. - 90% RH Charge amount 40.2 39.8
(-.mu.C/g)
[0117] When this developer was used to form toner images using a
commercial copying machine (selenium drum type), fogging-free vivid
magenta images with good thin line reproducibility, excellent
spectral characteristics, and transparency suitable for color
blending by superposing were obtained.
Example 10
[0118] Styrene-acrylic copolymer resin [ALMATEX CPR600B (trade
name), produced by Mitsui Chemicals, Inc.] . . . 100 parts [0119]
Carbon black [MA-100 (trade name), produced by Mitsubishi Chemical
Corporation] . . . 6 parts [0120] Low polymer polypropylene [Viscol
550-P (trade name), produced by Sanyo Chemical Industries, Ltd.] .
. . 5 parts [0121] Charge control agent (crystalline zinc
3,5-di-tert-butylsalicylate having major peaks of X-ray diffraction
using the CuK.alpha.-characteristic X-ray [wavelength 1.541 .ANG.]
at Bragg angles 2.theta. of at least 5.2.+-.0.2.degree.,
6.7.+-.0.2.degree., 7.7.+-.0.2.degree. and 15.7.+-.0.2.degree.) . .
. 1 part
[0122] The above ingredients were treated in the same manner as
Example 6 to yield a negatively chargeable black toner 10 to 20
.mu.m in particle diameter and a developer. Using this developer,
changes over time in charge amount and the environmental stability
of charge amount were determined in the same manner as Example 6.
The results are shown in Tables 9 and 10, respectively.
[0123] Changes Over Time in Charge Amount TABLE-US-00009 TABLE 9
Time (min) 1 3 5 10 15 30 Charge amount (-.mu.C/g) 23.1 25.2 26.6
27.0 27.2 27.6
[0124] Environmental Stability TABLE-US-00010 TABLE 10 5.degree. C.
- 30% RH 35.degree. C. - 90% RH Charge amount 27.3 26.8
(-.mu.C/g)
[0125] When this developer was used to form toner images using a
commercial copying machine (selenium drum type), fogging-free
high-quality images with good thin line reproducibility and good
charge stability and sustainability without image density reduction
were obtained. The offset phenomenon was never observed.
Comparative Example 1
[0126] A negatively chargeable black toner 10 to 20 .mu.m in
particle diameter and a developer were prepared in the same manner
as Example 6, except that an aluminum compound of
3,5-di-tert-butylsalicylic acid (charge control agent) was used in
place of the charge control resin particles. Using this developer,
changes over time in charge amount and the environmental stability
of charge amount were determined in the same manner as Example 6.
The results are shown in Tables 11 and 12, respectively.
[0127] Changes Over Time in Charge Amount TABLE-US-00011 TABLE 11
Time (min) 1 3 5 10 15 30 Charge amount (-.mu.C/g) 22.5 26.8 29.4
32.3 33.2 35.5
[0128] Environmental Stability TABLE-US-00012 TABLE 12 5.degree. C.
- 30% RH 35.degree. C. - 90% RH Charge amount 34.1 29.8
(-.mu.C/g)
* * * * *